target_spec_json/
lib.rs

1// SPDX-License-Identifier: Apache-2.0 OR MIT
2
3/*!
4<!-- Note: Document from sync-markdown-to-rustdoc:start through sync-markdown-to-rustdoc:end
5     is synchronized from README.md. Any changes to that range are not preserved. -->
6<!-- tidy:sync-markdown-to-rustdoc:start -->
7
8Structured access to rustc `--print target-spec-json` and `--print all-target-specs-json`.
9
10## Usage
11
12Add this to your `Cargo.toml`:
13
14```toml
15[dependencies]
16target-spec-json = "0.2"
17```
18
19## Compatibility
20
21Both `--print target-spec-json` and `--print all-target-specs-json` are unstable interfaces and may not work with certain version combinations of Rust versions and `target-spec-json` versions.
22
23The following combinations have been confirmed to work:
24
25| target-spec-json | Rust                                    |
26| ---------------- | --------------------------------------- |
27| 0.2.12           | nightly-2026-07-23                      |
28| 0.2.11           | nightly-2026-07-03 - nightly-2026-07-20 |
29| 0.2.10           | nightly-2026-06-27 - nightly-2026-06-28 |
30| 0.2.9            | nightly-2026-04-29 - nightly-2026-06-26 |
31| 0.2.8            | nightly-2026-03-26 - nightly-2026-04-29 |
32| 0.2.7            | nightly-2026-01-09 - nightly-2026-03-25 |
33| 0.2.6            | nightly-2025-11-29 - nightly-2026-01-08 |
34| 0.2.5            | nightly-2025-10-08 - nightly-2025-10-30 |
35| 0.2.4            | nightly-2025-09-23 - nightly-2025-10-07 |
36| 0.2.3            | nightly-2025-09-01 - nightly-2025-09-22 |
37| 0.2.2            | nightly-2025-08-31                      |
38| 0.2.1            | nightly-2025-08-10 - nightly-2025-08-30 |
39| 0.2.0            | nightly-2025-07-06 - nightly-2025-08-08 |
40
41## Related Projects
42
43- [cargo-config2]: Library to load and resolve Cargo configuration.
44
45[cargo-config2]: https://github.com/taiki-e/cargo-config2
46
47<!-- tidy:sync-markdown-to-rustdoc:end -->
48*/
49
50#![no_std]
51#![doc(test(
52    no_crate_inject,
53    attr(allow(
54        dead_code,
55        unused_variables,
56        clippy::undocumented_unsafe_blocks,
57        clippy::unused_trait_names,
58    ))
59))]
60#![forbid(unsafe_code)]
61#![warn(
62    // Lints that may help when writing public library.
63    missing_debug_implementations,
64    // missing_docs,
65    clippy::alloc_instead_of_core,
66    clippy::exhaustive_enums,
67    clippy::exhaustive_structs,
68    clippy::impl_trait_in_params,
69    clippy::std_instead_of_alloc,
70    clippy::std_instead_of_core,
71    // clippy::missing_inline_in_public_items,
72)]
73
74extern crate alloc;
75extern crate std;
76
77#[cfg(test)]
78#[path = "gen/tests/assert_impl.rs"]
79mod assert_impl;
80#[cfg(test)]
81#[path = "gen/tests/track_size.rs"]
82mod track_size;
83
84#[path = "gen/target_spec.rs"]
85mod target_spec;
86pub use self::target_spec::{
87    Arch, BinaryFormat, Env, Os, PanicStrategy, Sanitizer, TargetEndian, TargetFamily,
88};
89
90#[macro_use]
91mod process;
92
93mod error;
94
95use alloc::{collections::BTreeMap, string::String, vec::Vec};
96use core::ops;
97use std::process::Command;
98
99use serde_derive::{Deserialize, Serialize};
100
101pub use self::error::Error;
102use self::{error::Result, process::ProcessBuilder};
103
104pub type AllTargetSpecs = BTreeMap<String, TargetSpec>;
105
106// Refs:
107// - https://github.com/rust-lang/rust/blob/HEAD/compiler/rustc_target/src/spec/mod.rs
108// - https://github.com/rust-lang/rust/blob/c0bb3b98bb7aac24a37635e5d36d961e0b14f435/compiler/rustc_target/src/spec/json.rs
109// TODO: use https://github.com/rust-lang/rust/pull/144498
110
111#[derive(Debug, Clone, Serialize, Deserialize)]
112#[serde(rename_all = "kebab-case")]
113#[cfg_attr(test, serde(deny_unknown_fields))]
114#[non_exhaustive]
115pub struct TargetSpec {
116    #[serde(skip_serializing_if = "Option::is_none")]
117    pub abi_return_struct_as_int: Option<bool>,
118    #[serde(skip_serializing_if = "Option::is_none")]
119    pub abi: Option<String>,
120    #[serde(skip_serializing_if = "Option::is_none")]
121    pub allows_weak_linkage: Option<bool>,
122    pub arch: Arch,
123    #[serde(skip_serializing_if = "Option::is_none")]
124    pub archive_format: Option<String>,
125    #[serde(skip_serializing_if = "Option::is_none")]
126    pub asm_args: Option<Vec<String>>,
127    #[serde(default = "default_true", skip_serializing_if = "Clone::clone")]
128    pub atomic_cas: bool,
129    #[serde(default, skip_serializing_if = "BinaryFormat::is_elf")]
130    pub binary_format: BinaryFormat,
131    #[serde(skip_serializing_if = "Option::is_none")]
132    pub bitcode_llvm_cmdline: Option<String>,
133    #[serde(skip_serializing_if = "Option::is_none")]
134    pub c_enum_min_bits: Option<u32>,
135    #[serde(skip_serializing_if = "Option::is_none")]
136    pub code_model: Option<String>,
137    #[serde(skip_serializing_if = "Option::is_none")]
138    pub cpu: Option<String>,
139    #[serde(skip_serializing_if = "Option::is_none")]
140    pub crt_objects_fallback: Option<String>,
141    #[serde(skip_serializing_if = "Option::is_none")]
142    pub crt_static_allows_dylibs: Option<bool>,
143    #[serde(skip_serializing_if = "Option::is_none")]
144    pub crt_static_default: Option<bool>,
145    #[serde(skip_serializing_if = "Option::is_none")]
146    pub crt_static_respected: Option<bool>,
147    pub data_layout: String,
148    #[serde(skip_serializing_if = "Option::is_none")]
149    pub debuginfo_kind: Option<String>,
150    #[serde(skip_serializing_if = "Option::is_none")]
151    pub default_adjusted_cabi: Option<String>,
152    #[serde(skip_serializing_if = "Option::is_none")]
153    pub default_codegen_units: Option<u32>,
154    #[serde(skip_serializing_if = "Option::is_none")]
155    pub default_dwarf_version: Option<u32>,
156    #[serde(skip_serializing_if = "Option::is_none")]
157    pub default_hidden_visibility: Option<bool>,
158    #[serde(skip_serializing_if = "Option::is_none")]
159    pub default_sanitizers: Option<Vec<Sanitizer>>,
160    #[serde(skip_serializing_if = "Option::is_none")]
161    pub default_uwtable: Option<bool>,
162    #[serde(skip_serializing_if = "Option::is_none")]
163    pub direct_access_external_data: Option<bool>,
164    #[serde(skip_serializing_if = "Option::is_none")]
165    pub disable_redzone: Option<bool>,
166    #[serde(skip_serializing_if = "Option::is_none")]
167    pub dll_prefix: Option<String>,
168    #[serde(skip_serializing_if = "Option::is_none")]
169    pub dll_suffix: Option<String>,
170    #[serde(skip_serializing_if = "Option::is_none")]
171    pub dll_tls_export: Option<bool>,
172    #[serde(skip_serializing_if = "Option::is_none")]
173    pub dynamic_linking: Option<bool>,
174    #[serde(skip_serializing_if = "Option::is_none")]
175    pub eh_frame_header: Option<bool>,
176    #[serde(skip_serializing_if = "Option::is_none")]
177    pub emit_debug_gdb_scripts: Option<bool>,
178    #[serde(skip_serializing_if = "Option::is_none")]
179    pub entry_abi: Option<String>,
180    #[serde(skip_serializing_if = "Option::is_none")]
181    pub entry_name: Option<String>,
182    #[serde(default, skip_serializing_if = "Env::is_none")]
183    pub env: Env,
184    #[serde(skip_serializing_if = "Option::is_none")]
185    pub executables: Option<bool>,
186    #[serde(skip_serializing_if = "Option::is_none")]
187    pub exe_suffix: Option<String>,
188    #[serde(skip_serializing_if = "Option::is_none")]
189    pub features: Option<String>,
190    #[serde(skip_serializing_if = "Option::is_none")]
191    pub force_emulated_tls: Option<bool>,
192    #[serde(skip_serializing_if = "Option::is_none")]
193    pub forces_embed_bitcode: Option<bool>,
194    #[serde(skip_serializing_if = "Option::is_none")]
195    pub frame_pointer: Option<String>,
196    #[serde(skip_serializing_if = "Option::is_none")]
197    pub function_sections: Option<bool>,
198    #[serde(skip_serializing_if = "Option::is_none")]
199    pub generate_arange_section: Option<bool>,
200    #[serde(skip_serializing_if = "Option::is_none")]
201    pub has_rpath: Option<bool>,
202    #[serde(skip_serializing_if = "Option::is_none")]
203    pub has_thread_local: Option<bool>,
204    #[serde(default, skip_serializing_if = "ops::Not::not")]
205    pub has_thumb_interworking: bool,
206    #[serde(default, skip_serializing_if = "ops::Not::not")]
207    pub is_builtin: bool,
208    #[serde(default, skip_serializing_if = "ops::Not::not")]
209    pub is_like_android: bool,
210    #[serde(default, skip_serializing_if = "ops::Not::not")]
211    pub is_like_aix: bool,
212    #[serde(default, skip_serializing_if = "ops::Not::not")]
213    pub is_like_darwin: bool,
214    #[serde(default, skip_serializing_if = "ops::Not::not")]
215    pub is_like_gpu: bool,
216    /// replaced by `is_like_darwin`
217    #[serde(default, skip_serializing_if = "ops::Not::not")]
218    pub is_like_osx: bool,
219    #[serde(default, skip_serializing_if = "ops::Not::not")]
220    pub is_like_solaris: bool,
221    #[serde(default, skip_serializing_if = "ops::Not::not")]
222    pub is_like_msvc: bool,
223    #[serde(default, skip_serializing_if = "ops::Not::not")]
224    pub is_like_vexos: bool,
225    #[serde(default, skip_serializing_if = "ops::Not::not")]
226    pub is_like_wasm: bool,
227    #[serde(default, skip_serializing_if = "ops::Not::not")]
228    pub is_like_windows: bool,
229    #[serde(skip_serializing_if = "Option::is_none")]
230    pub late_link_args: Option<BTreeMap<String, Vec<String>>>,
231    #[serde(skip_serializing_if = "Option::is_none")]
232    pub late_link_args_dynamic: Option<BTreeMap<String, Vec<String>>>,
233    #[serde(skip_serializing_if = "Option::is_none")]
234    pub late_link_args_static: Option<BTreeMap<String, Vec<String>>>,
235    #[serde(skip_serializing_if = "Option::is_none")]
236    pub limit_rdylib_exports: Option<bool>,
237    #[serde(skip_serializing_if = "Option::is_none")]
238    pub link_env: Option<Vec<String>>,
239    #[serde(skip_serializing_if = "Option::is_none")]
240    pub link_env_remove: Option<Vec<String>>,
241    #[serde(skip_serializing_if = "Option::is_none")]
242    pub link_self_contained: Option<BTreeMap<String, Vec<String>>>,
243    #[serde(skip_serializing_if = "Option::is_none")]
244    pub link_script: Option<String>,
245    #[serde(skip_serializing_if = "Option::is_none")]
246    pub linker: Option<String>,
247    #[serde(skip_serializing_if = "Option::is_none")]
248    pub linker_flavor: Option<String>,
249    #[serde(skip_serializing_if = "Option::is_none")]
250    pub linker_is_gnu: Option<bool>,
251    #[serde(skip_serializing_if = "Option::is_none")]
252    pub lld_flavor: Option<String>,
253    #[serde(skip_serializing_if = "Option::is_none")]
254    pub llvm_abiname: Option<String>,
255    #[serde(skip_serializing_if = "Option::is_none")]
256    pub llvm_args: Option<Vec<String>>,
257    #[serde(skip_serializing_if = "Option::is_none")]
258    pub llvm_floatabi: Option<String>,
259    #[serde(skip_serializing_if = "Option::is_none")]
260    pub llvm_mcount_intrinsic: Option<String>,
261    pub llvm_target: String,
262    #[serde(skip_serializing_if = "Option::is_none")]
263    pub main_needs_argc_argv: Option<bool>,
264    #[serde(skip_serializing_if = "Option::is_none")]
265    pub max_atomic_width: Option<u32>,
266    #[serde(skip_serializing_if = "Option::is_none")]
267    pub merge_functions: Option<String>,
268    pub metadata: Option<Metadata>,
269    #[serde(skip_serializing_if = "Option::is_none")]
270    pub min_atomic_width: Option<u32>,
271    #[serde(skip_serializing_if = "Option::is_none")]
272    pub min_global_align: Option<u32>,
273    #[serde(skip_serializing_if = "Option::is_none")]
274    pub need_explicit_cpu: Option<bool>,
275    #[serde(skip_serializing_if = "Option::is_none")]
276    pub needs_plt: Option<bool>,
277    #[serde(skip_serializing_if = "Option::is_none")]
278    pub no_builtins: Option<bool>,
279    #[serde(skip_serializing_if = "Option::is_none")]
280    pub no_default_libraries: Option<bool>,
281    #[serde(default, skip_serializing_if = "Os::is_none")]
282    pub os: Os,
283    #[serde(skip_serializing_if = "Option::is_none")]
284    pub obj_is_bitcode: Option<bool>,
285    #[serde(skip_serializing_if = "Option::is_none")]
286    pub only_cdylib: Option<bool>,
287    #[serde(skip_serializing_if = "Option::is_none")]
288    pub override_export_symbols: Option<Vec<String>>,
289    #[serde(default, skip_serializing_if = "PanicStrategy::is_unwind")]
290    pub panic_strategy: PanicStrategy,
291    #[serde(skip_serializing_if = "Option::is_none")]
292    pub plt_by_default: Option<bool>,
293    #[serde(skip_serializing_if = "Option::is_none")]
294    pub position_independent_executables: Option<bool>,
295    #[serde(skip_serializing_if = "Option::is_none")]
296    pub post_link_args: Option<BTreeMap<String, Vec<String>>>,
297    #[serde(skip_serializing_if = "Option::is_none")]
298    pub post_link_objects: Option<BTreeMap<String, Vec<String>>>,
299    #[serde(skip_serializing_if = "Option::is_none")]
300    pub post_link_objects_fallback: Option<BTreeMap<String, Vec<String>>>,
301    #[serde(skip_serializing_if = "Option::is_none")]
302    pub pre_link_args: Option<BTreeMap<String, Vec<String>>>,
303    #[serde(skip_serializing_if = "Option::is_none")]
304    pub pre_link_objects: Option<BTreeMap<String, Vec<String>>>,
305    #[serde(skip_serializing_if = "Option::is_none")]
306    pub pre_link_objects_fallback: Option<BTreeMap<String, Vec<String>>>,
307    #[serde(skip_serializing_if = "Option::is_none")]
308    pub relax_elf_relocations: Option<bool>,
309    #[serde(skip_serializing_if = "Option::is_none")]
310    pub relocation_model: Option<String>,
311    #[serde(skip_serializing_if = "Option::is_none")]
312    pub relro_level: Option<String>,
313    #[serde(skip_serializing_if = "Option::is_none")]
314    pub requires_consistent_cpu: Option<bool>,
315    #[serde(skip_serializing_if = "Option::is_none")]
316    pub requires_lto: Option<bool>,
317    #[serde(skip_serializing_if = "Option::is_none")]
318    pub requires_uwtable: Option<bool>,
319    #[serde(skip_serializing_if = "Option::is_none")]
320    pub rustc_abi: Option<String>,
321    #[serde(skip_serializing_if = "Option::is_none")]
322    pub split_debuginfo: Option<String>,
323    #[serde(skip_serializing_if = "Option::is_none")]
324    pub stack_probes: Option<StackProbes>,
325    #[serde(skip_serializing_if = "Option::is_none")]
326    pub static_initializer_must_be_acyclic: Option<bool>,
327    #[serde(skip_serializing_if = "Option::is_none")]
328    pub static_position_independent_executables: Option<bool>,
329    #[serde(skip_serializing_if = "Option::is_none")]
330    pub staticlib_prefix: Option<String>,
331    #[serde(skip_serializing_if = "Option::is_none")]
332    pub staticlib_suffix: Option<String>,
333    #[serde(default, skip_serializing_if = "Vec::is_empty")]
334    pub supported_sanitizers: Vec<Sanitizer>,
335    #[serde(default, skip_serializing_if = "Vec::is_empty")]
336    pub supported_split_debuginfo: Vec<String>,
337    #[serde(default = "default_true", skip_serializing_if = "Clone::clone")]
338    pub supports_stack_protector: bool,
339    #[serde(default, skip_serializing_if = "ops::Not::not")]
340    pub supports_fentry: bool,
341    #[serde(default, skip_serializing_if = "ops::Not::not")]
342    pub supports_xray: bool,
343    #[serde(skip_serializing_if = "Option::is_none")]
344    pub simd_types_indirect: Option<bool>,
345    #[serde(default, skip_serializing_if = "ops::Not::not")]
346    pub singlethread: bool,
347    #[serde(default, skip_serializing_if = "TargetEndian::is_little")]
348    pub target_endian: TargetEndian,
349    #[serde(default, skip_serializing_if = "Vec::is_empty")]
350    pub target_family: Vec<TargetFamily>,
351    #[serde(skip_serializing_if = "Option::is_none")]
352    pub target_mcount: Option<String>,
353    // Integer since 1.89
354    #[serde(skip_serializing_if = "Option::is_none")]
355    pub target_c_int_width: Option<u32>,
356    // Integer since 1.91
357    pub target_pointer_width: u32,
358    #[serde(skip_serializing_if = "Option::is_none")]
359    pub tls_model: Option<String>,
360    #[serde(skip_serializing_if = "Option::is_none")]
361    pub trap_unreachable: Option<bool>,
362    #[serde(default, skip_serializing_if = "Vec::is_empty")]
363    pub unsupported_cpus: Vec<String>,
364    #[serde(skip_serializing_if = "Option::is_none")]
365    pub use_ctors_section: Option<bool>,
366    #[serde(skip_serializing_if = "Option::is_none")]
367    pub vendor: Option<String>,
368}
369
370#[derive(Debug, Clone, Serialize, Deserialize)]
371#[cfg_attr(test, serde(deny_unknown_fields))]
372#[non_exhaustive]
373pub struct Metadata {
374    pub description: Option<String>,
375    pub host_tools: Option<bool>,
376    pub std: Option<bool>,
377    pub tier: Option<u32>,
378}
379
380#[derive(Debug, Clone, Serialize, Deserialize)]
381#[serde(rename_all = "kebab-case")]
382#[cfg_attr(test, serde(deny_unknown_fields))]
383#[non_exhaustive]
384pub struct StackProbes {
385    pub kind: String,
386    #[serde(skip_serializing_if = "Option::is_none")]
387    pub min_llvm_version_for_inline: Option<(u32, u32, u32)>,
388}
389
390fn default_true() -> bool {
391    true
392}
393
394/// `<rustc> -Z unstable-options --print target-spec-json --target <target>`
395pub fn target_spec_json(rustc: Command, target: &str) -> Result<TargetSpec> {
396    let raw = ProcessBuilder::from_std(rustc)
397        .args(["-Z", "unstable-options", "--print", "target-spec-json", "--target", target])
398        .read()?;
399    serde_json::from_str(&raw).map_err(Error::new)
400}
401
402/// `<rustc> -Z unstable-options --print all-target-specs-json`
403pub fn all_target_specs_json(rustc: Command) -> Result<AllTargetSpecs> {
404    let raw = ProcessBuilder::from_std(rustc)
405        .args(["-Z", "unstable-options", "--print", "all-target-specs-json"])
406        .read()?;
407    serde_json::from_str(&raw).map_err(Error::new)
408}
409
410#[cfg(test)]
411mod tests {
412    use std::eprintln;
413
414    use super::*;
415
416    fn target_spec_json(target: &str) -> Result<(TargetSpec, String)> {
417        let mut cmd = cmd!(
418            "rustc",
419            "-Z",
420            "unstable-options",
421            "--print",
422            "target-spec-json",
423            "--target",
424            target
425        );
426        if !rustversion::cfg!(nightly) {
427            cmd.env("RUSTC_BOOTSTRAP", "1");
428        }
429        let raw = cmd.read()?;
430        Ok((serde_json::from_str(&raw).map_err(Error::new)?, raw))
431    }
432
433    fn all_target_specs_json() -> Result<(AllTargetSpecs, String)> {
434        let mut cmd = cmd!("rustc", "-Z", "unstable-options", "--print", "all-target-specs-json");
435        if !rustversion::cfg!(nightly) {
436            cmd.env("RUSTC_BOOTSTRAP", "1");
437        }
438        let raw = cmd.read()?;
439        Ok((serde_json::from_str(&raw).map_err(Error::new)?, raw))
440    }
441
442    // Skip pre-1.91 because target-pointer-width change
443    #[rustversion::attr(before(1.91), ignore)]
444    #[test]
445    #[cfg_attr(miri, ignore)] // Miri doesn't support std::process::Command: https://github.com/rust-lang/miri/issues/3374
446    fn parse_target_spec_json() {
447        // builtin targets
448        for target in cmd!("rustc", "--print", "target-list").read().unwrap().lines() {
449            eprintln!("target={target}:");
450            let (parsed, raw) = target_spec_json(target).unwrap();
451            let deserialized = serde_json::to_string(&parsed).unwrap();
452            assert_eq!(
453                serde_json::from_str::<serde_json::Value>(&raw).unwrap(),
454                serde_json::from_str::<serde_json::Value>(&deserialized).unwrap()
455            );
456        }
457        eprintln!("all-targets:");
458        let (parsed, raw) = all_target_specs_json().unwrap();
459        let deserialized = serde_json::to_string(&parsed).unwrap();
460        assert_eq!(
461            serde_json::from_str::<serde_json::Value>(&raw).unwrap(),
462            serde_json::from_str::<serde_json::Value>(&deserialized).unwrap()
463        );
464        // TODO: custom targets
465        // for spec_path in fs::read_dir(fixtures_path().join("target-specs"))
466        //     .unwrap()
467        //     .map(|e| e.unwrap().path())
468        // {
469        // }
470    }
471}
target_spec_json/lib.rs

target_spec_json/
lib.rs
